A stent delivery system is a medical device used for improving a stenosis or occluded part in a lumen in a living body. The stent delivery system is provided with an inflatable balloon which is disposed on the outer circumference of a distal end portion of a hollow shaft section, and a stent which is composed of wavy linear members, is disposed on the outer circumference of the balloon and is expanded by inflation of the balloon.
The stent is caulked (mounted) onto the balloon while the balloon is in a radially contracted state. After arrival in a target part (stenosis or occluded part), the balloon is inflated to bring the stent into plastic deformation, whereby the stent is put indwelling (indwelled) in secure contact with the inner surface of the target part. In this instance, depending on the state of the target part or the way in which the balloon is inflated, the stent may fail to spread uniformly in the circumferential direction, so that the stent may be unable to display its intended performance.
In consideration of the above-mentioned problem, for example, there is a stent wherein apex parts (opposed stop surfaces) of linear members (struts) are engaged with each other so that hinge regions of the linear members will not be opened in excess of a predetermined angle, whereby nonuniform expansion of the stent in the circumferential direction is prevented. An example of this stent is disclosed in Japanese Application Publication No. 2000-516486.
However, the material thickness of a stent is in general extremely small, about 100 μm. In addition, a stent in practical use receives forces in various directions from a blood vessel wall or the like. In the stents like the one disclosed in Japanese Application Publication No. 2000-516486, therefore, it may be difficult to successfully achieve the intended engagement, and the stent may be expanded nonuniformly. Thus, there has been the problem that nonuniform expansion of the stent cannot be avoided assuredly.